Monday, October 29, 2007

Our ever-changing world: migrating land masses

From a packet of Instant Quaker Oatmeal:

Q. On what continent did dinosaurs first appear?

A. Trick question! All the continents were joined together during the Early Triassic period in one big continent called Pangaea.

Source: Encyclopedia Britannica

I think one of my favorite memories from school days was the day we got to Pangaea in our textbook. You could look at a globe, or even a map (if you were good at adjusting for the distortions in map projections) and see how continents fit together if you scrunched them back together in your mind. I didn't even need the further evidence of matching rock formations along different shorelines to make me believe this theory.

We had a lot of fun, as I recall, playing with the mental gymnastics that naturally followed from the idea of one bigger land mass breaking up, with the parts heading off in different directions. For starters, animal and plant populations would be severed. And then the following generations of plants and animals on each traveling continent would have to adjust to the slow, slow, but big, big changes that would occur. The latitude as well as the longitude would change, and with it seasons and daylight and temps and who knows what all? Plus, the ocean currents would have to change as the land masses moved around, moving the blockades, as it were. This would, as I understand it, make for big changes in weather patterns.

And then, when you also started factoring in the growth of new land, thanks to volcanoes, etc., it got really interesting. For instance, the evidence pointed to North America and South America not being joined at first, but being linked after volcanoes in what is now Central America built up the land bridge that is there today. Can you imagine what a difference that had to make in climate, not to mention to ocean plant and animal populations? I mean, the Pacific and Atlantic oceans were linked there, and then they weren't. I've been led to believe that this happened slowly, but still... I saw a television documentary on this once, and it showed an animation of ocean currents swishing through there, and then being blocked and therefore totally, drastically rerouted. I hope it was an accurate rendition, because it made a big impression on me. The oceans got cut in two, but land animals had new lands made available for migration. Such a deal.

For another instance, where I live used to be practically a rain forest (you should see our fossils around here - what a fascinating story they tell), but ever since the Cascade Mountains grew up, this part of the world has been in a rain shadow (that is, we don't get much rain because of the mountains to our west). And I'm sure the wind patterns are different, too. Certainly the seasons are more extreme than they used to be. And...

But you get the picture, I'm sure. To try to approach a comprehension of reality, start with the above and start factoring in everyday sorts of erosion, not to mention drastic changes from earthquakes and floods, and then try to factor in the natural evolution of ecosystems as soils mature, and then...

Well, you get the picture, I'm sure. The histories of the physical and biological worlds can be hard to get one's head around. But it can be fun to try.

Have you ever tried to map what's happened to the spot where you live? How it's (probably) migrated over the globe over the eons? I don't know of any computer games or models for this, but I think they'd be fun to play with. At a guess, you could set your imaginary self down in the tropics and travel to the temperate zone without ever standing up, if you factored in enough time, and picked the right starting point.

OK, yes, perhaps it might be somewhat-geeky fun, but I like somewhat geeky fun. Heh.

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